ok trying to help a friend bike ran great three sundays ago. lsst night getting ready to ride this week end we start the bike and problems hard to start, runs on one side and left side back fires through pipe we tryed to take it down the strreet to clean it out. the left side back fire an flame shoot out the pipe...... tried three diffrent carbs same thing, some one has cut wire to tores but we swithed plug wire and no change any help?????????????????????